Tensioner Mismatch With Housing

[drdoom]

Planning to convert from semi-auto to manual cambelt tensioner I have purchased a new eccentric hub which, oddly, is of greater OD than is the ID of bore in my crank seal housing. Were there early housings whose hub bores differ from those in the later engines?

Cheers

[EXCEL V8]

The early manual hubs are different from the later ones wrt to bearing - the early ones used two bearings with a steel sleeve pressed on.  The later type use a sealed double row bearing.  I've got both types but they both measure 13/16" across the part that sits in the crank seal housing, so there may be a third type - ISTR that the Jensen Healeys might be different.

Pete

[drdoom]

Believe we have this sussed. Review of SJ's offerings show differing parts for Excel as compared to early Esprit eccentric hub. Oddly, my S2 engine had been drilled and tapped for the eccentric stud though equipped with the semi-auto kit as one would expect.

Cheers

[Lou R]

Steve,

I went the other way with my car (manual back to semi-auto tensioner).  I put the manual tensioner parts in a box so they're sitting on a shelf.  I'll measure the OD tomorrow and get back to you.

Lou R

[Lou R]

I also measured 13/16".

Lou R

[drdoom]

My new hub also measures .812 or 13/16, though the housing bore is on the order of .766. Intrigued that this hub came accompanied by a steel collar, as seen in the attached pic. Primary PC is getting its head sorted at the shop, once recovered I'll be able to review the ultimate Service Parts List archived within, rather expecting to find the collar accounted for in the process.

Cheers

[Lou R]

Steve,

Just to confirm that Lotus used a different crank seal housing on manual vs. semi-auto tensioners.  If you don't have the correct housing that is specifically for the manual tensioner it will never work.

Lou R

[drdoom]

Altogether clear from the start. What we are discussing is a crank seal housing of the sort including a bore for locating the eccentric. What is odd is that the bore is too small for the hub in hand. I also have a housing cast without material where it would be required for the eccentric, so both types are familiar.

Cheers

[drdoom]

Well something of an "A-Ha" moment today when inspecting and contemplating the bits. Regarding the collar as both bearing and locating surface seems to make sense, in that the neat slip fit will not vary with temperature, both it and the hub being plated steel. With an altogether novel serpentine belt drive planned for my S2 ancillaries it makes sense to carry all in a bespoke plate, 1/2 AL in this case, which will replace both the OEM crank seal housing and water pump therefore facilitating support by an array of fixing points in the cylinder block face. With the eccentric hub stud centre precisely located a bore would then be machined for interference fit of the collar in the plate.

Cheers

[mike.griese]

Wait - you want to combine the water pump with the front cover?  Wouldn't that mean replacing the front seal along with the pump and resealing both the oil system and the coolant system if you had to service either?

[drdoom]

It's because I am attempting to fit a dry sump 910 bottom end into the early chassis that the change to ancillary drive and mountings has arisen. The water pump is to be changed out to electric, likely relocated to the front chassis area aft of the rad. By all accounts any service work in the forward area of the engine bay is best done in the shop, so I am striving to minimise any chance of fails when afield.

Cheers

[Andyww]

On the 910 engines the front cover is no different if tensioner is manual or semi auto. The round part of the tensioner sits in the AC compressor bracket or if no AC, (And I guess on dry sump where the AC was on the other side) there is a small bracket which doesnt have the compressor mountings.

The block has an extra tapped hole of course for the manual.

To be more accurate the 910 never had the manual, only came with 912 engines and the part number of the eccentric has a 912 prefix so is different from the old one on early 907 which they swapped out owing to belt jumping issues.

[Andyww]

On 13/01/2023 at 14:35, Lou R said:

Steve,

Just to confirm that Lotus used a different crank seal housing on manual vs. semi-auto tensioners.  If you don't have the correct housing that is specifically for the manual tensioner it will never work.

Lou R

Its almost a routine task converting a semi-auto to manual. Lotusbits do it on all their rebuilds and the front cover is not changed. Its a case of using the 912 engine spec parts. You might be referring to trying to use very early 907 spec parts.

[EXCEL V8]

Have you chosen the water pump yet Steve?  I decided to fit a big one (150 litres per min ISTR) when I ran the LS1 in the Excel and I could never achieve stable temps - I suspect there was just too much circulation even using the controller that came with it.  When I swapped back to the original engine-driven pump I had no problems, even on the track.  I still like the idea of electric pumps but sizing it seems tricky!  There is a guy over on The Lotus Grand Tourers site who has one working well in his Excel though, and swears by it.

Pete

[drdoom]

Hi Pete,

I am very near ordering a Davies-Craig pump, rated 115 l/min as I recall, their recommendation for engines between 2 and 3.5l. Inclined to think Aussies know their stuff when it comes to engine cooling. Basic though my Haltech ECU may be it should serve via digital pulsed output to drive the pump by way of a repurposed cooling fan controller, as are commonly found on modern cars.

Cheers